interface mess (again)
The way I like to use to close windows is right click the little border between two, and then press Join. You will know when you can right click as you hover over the border and your mouse becomes a partition. Then click one of the two windows that you want to join and they both become one. 

The window you click will turn into part of the one you didn't click, merging into one.

In my opinion, this is much better because it allows you to preserve the state of one window.

If you want to open a window again, just move your mouse to a corner until it becomes a crosshair, and drag it to the correct size. Hope this helps!